Animals such as mammals and birds are often susceptible to parasite infestations/infections. These parasites may be ectoparasites, such as fleas, ticks and parasitic flies, and endoparasites such as nematodes and other worms. Domesticated animals, such as cats and dogs, are often infested with one or more of the following ectoparasites:                fleas (e.g. Ctenocephalides spp., such as Ctenocephalides felis and the like);        ticks (e.g. Rhipicephalus spp., Ixodes spp., Dermacentor spp., Amblyomma spp., and the like);        mites (e.g. Demodex spp., Sarcoptes spp., Otodectes spp., and the like);        lice (e.g. Trichodectes spp., Cheyletiella spp., Linognathus spp. and the like);        mosquitoes (Aedes spp., Culex spp., Anopheles spp. and the like); and        flies (Haematobia spp., Musca spp., Stomoxys spp., Dermatobia spp., Cochliomyia spp. and the like).        
Fleas are a particular problem because not only do they adversely affect the health of the animal or human, but they also cause a great deal of psychological stress. Moreover, fleas may also transmit pathogenic agents to animals and humans, such as tapeworm (Dipylidium caninum).
Similarly, ticks are also harmful to the physical and psychological health of the animal or human. However, the most serious problem associated with ticks is that they are vectors of pathogenic agents in both humans and animals. Major diseases which may be transmitted by ticks include borrelioses (Lyme disease caused by Borrelia burgdorferi), babesiosis (or piroplasmoses caused by Babesia spp.) and rickettsioses (e.g. Rocky Mountain spotted fever). Ticks also release toxins which cause inflammation or paralysis in the host. Occasionally, these toxins are fatal to the host.
Likewise, farm animals are also susceptible to parasite infestations. For example, cattle are affected by a large number of parasites. A parasite which is prevalent among cattle in some regions are ticks of the genus Rhipicephalus, especially those of the species microplus (cattle tick), decoloratus and annulatus. Ticks such as Rhipicephalus microplus (formerly Boophilus microplus) are difficult to control because they lay eggs in the pasture where farm animals graze. This species of ticks is considered a one-host tick and spends immature and adult stages on one animal before the female engorges and falls off the host to lay eggs in the environment. The life cycle of the tick is approximately three to four weeks. In addition to cattle, Rhipicephalus microplus may infest buffalo, horses, donkeys, goats, sheep, deer, pigs, and dogs. A heavy tick burden on animals can decrease production and damage hides as well as transmit diseases such as babesiosis (“cattle fever”) and anaplasmosis.
Animals and humans also suffer from endoparasitic infections including, for example, helminthiasis which is caused by of parasitic worms categorized as cestodes (tapeworm), nematodes (roundworm) and trematodes (flatworm or flukes). These parasites adversely affect the nutrition of the animal and cause severe economic losses in pigs, sheep, horses, and cattle as well as affecting companion animals and poultry. Other parasites which occur in the gastrointestinal tract of animals and humans include Ancylostoma, Necator, Ascaris, Strongyloides, Trichinella, Capillaria, Toxocara, Toxascaris, Trichuris, Enterobius and parasites which are found in the blood or other tissues and organs such as filarial worms and the extra intestinal stages of Strongyloides, Toxocara and Trichinella. 
Recently, isoxazole and isoxazoline-containing compounds have been demonstrated to be effective against parasites that harm animals. For example, U.S. Pat. No. 7,964,204 (to DuPont, incorporated by reference herein in its entirety) discloses isoxazoline compounds according to Formula (I) below, which are active against ectoparasites and/or endoparasites.
In addition, published patent application nos. US 2010/0254960 A1, WO 2007/070606 A2, WO 2007/123855 A2, WO 2010/003923 A1, U.S. Pat. Nos. 7,951,828 & 7,662,972, US 2010/0137372 A1, US 2010/0179194 A2, US 2011/0086886 A2, US 2011/0059988 A1, US 2010/0179195 A1 and WO 2007/075459 A2 and U.S. Pat. Nos. 8,410,153; 7,947,171; 8,618,126; 8,466,115; 8,383,659; 8,853,186; 7,951,828 and 7,662,972 (all incorporated herein by reference in their entirety) describe various other parasiticidal isoxazoline compounds. Other published patent applications that describe various other parasiticidal isoxazoline compounds and formulations comprising the same include WO 2007/079162 A1, WO 2008/154528 A1, WO 2009/002809 A2, WO 2011/149749 A1, WO 2013/078070, WO 2014/439475 A1, U.S. Pat. No. 8,466,115, WO 2012/120399, WO 2014/039484, WO 2014/189837, (Zoetis) and WO2012 120135A1 (Novartis). WO 2012/089623 describes topical localized isoxazoline formulations comprising glycofurol. WO 2013/039948 A1 provides for topical veterinary compositions comprising at least one isoxazoline active agent and WO 2013/119442 A1 provides for oral veterinary compositions such as a soft chew which comprising at least one isoxazoline active agent. All of the publications above are incorporated herein by reference in their entirety.
In additional to topical and oral dosage forms, it is sometimes possible to formulate active agents as long-acting formulations, depending upon, for example, the physiochemical properties of the individual active agent; these properties include, for example, solubility, bioavailability, etc. For example, U.S. Pat. Nos. 6,733,767 and 8,362,086 (both incorporated herein by reference in their entirety) provide for long acting injectable formulations comprising a bioactive substance, such as, for example, an avermectin or a milbemycin and a biological acceptable polymer.
Notwithstanding the compositions comprising isoxazoline active agents alone or in combination with other active agents described in the documents above, there is a need for veterinary compositions and methods with improved efficacy, bioavailability, and spectrum of coverage to protect animals against endoparasites and/or ectoparasites. More specifically, there is a need to develop a long-acting injectable formulation comprising an isoxazoline compound, which has good bioavailability and exhibits a reduced irritation at the injection site while still being effective against parasites (e.g., fleas and ticks) for a long duration (e.g., from three (3) to six (6) months or longer).